Part 12 (2/2)

On double lines each set of rails has its own separate signals, and drivers travelling on the ”up” line take no notice of signals nal-box usually controls three signals on each set of rails--the distant, the hoathered fro 92, which shows a station on a double line Between the distant and the home an interval is allowed of 800 yards on the level, 1,000 yards on a falling gradient, and 600 yards on a rising gradient The home stands near the approach end of the station, and the starting at the departure end of the platfor” signal some distance farther on

It should be noted that the distant is only a _caution_ signal, whereas both honals This means that when the driver sees the distant ”on,” he does not stop his train, but slackens speed, and prepares to stop at the honal Heif they are at danger In short, the distant merely warns the driver of what he e if a driver should overrun the home, it has been laid down that no train shall be allowed to pass the starting signal of one box unless the line is clear to a point at least a quarter of a mile beyond the home of the next box That point is called the _standard clearing point_

Technically described, a _block_ is a length of line between the last stop signal worked fronal worked fronal-box in advance

[Illustration: FIG 92--Showing position of signals Those at the top are ”off”]

INTERLOCKING SIGNALS

A signalnals to their normal positions in any order he likes He is co and ho and hoht, after the passage of a train, restore the hoet all about the distant, so that the next train, which he wants to stop, would dash past the distant without warning and have to pull up suddenly when the hoe until the distant is at danger; and, _vice versa_, he cannot lower the last until the other two are off This ear_

LOOKING GEAR

There are ear in use It is iive particulars of an elaborate locking-frame of any one type But if we confine ourselves to the si apparatus, such as is used in set an insight into the general principles of these safety devices, as the same principles underlie thenal lever and its connections Tothe catch-rod frouides; R R, anti-friction rollers; S, sockets for catch-rod to work in]

The levers in the particular type of locking gear which we are considering have each a tailpiece or ”tappet arm” attached to it, whichat right angles to this tappet, and close to it, either under or above, are the lock bars, or stud bars Refer now to Fig 94, which shows the ends of the three tappet arms, D, H, and S, crossed by a bar, B, from which project these studs The levers are all forward and the signals all ”on” If the signale, as it were, he would fail to es with a notch in D Before this stud can be got free of the notch the tappets H and Stheir notches in line with studs _b_ and _c_ (Fig 95) The signalman can now move D, since the notch easily pushes the stud _a_ to the left (Fig

96) The signals er As H and S are back-locked by D--that is, prevented by D fro put back into their nor of the three signals described is nals

[Illustration: FIG 94]

[Illustration: FIG 95]

On entering a signal-box a visitor will notice that the levers have different colours:--_Green_, signifying distant signals; _red_, signifying ho points; _black_, signifying trailing points; _white_, signifying spare levers

These different colours help the signalht levers easily

To the front of each lever is attached a sures on the top, then a line, and other nue number is that of the lever itself; the others, called _leads_, refer to levers which must be pulled before that particular lever can be released

[Illustration: FIG 96]

[Illustration: FIG 97--Model signal equip school

(By perazine”)]

POINTS

Mention wasfurther ill glance at the action of these devices for enabling a train to run fros 98 and 99 show the points at a simple junction It will be noticed that the rails of the line to the left of the points are continued as the outer rails of the main and branch lines The inner rails come to a sharp V-point, and to the left of this are the two short rails which, byportions, decide the direction of a train's travel In Fig 98 theparts are kept properly spaced by cross bars (or tie-rods), A A